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Food Chemistry 2 > Food Flavours > Flashcards

Food Flavours Flashcards

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1
Q

what are sensations produced by food in the mouth and nose?

A

taste: sweet, sour, salty, bitter, umami
odor: pungent, putrid, floral, ehtereal, minty, musty, camphoraceous
mouthfeel: pain, temp, tactile sensation

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2
Q

how are flavours perceived?

A

interactions between nasal cavity, receptors in mouth, teeth and jaws sends signals to the CNS for translation into what flavours are perceived

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3
Q

what is found in food that elicites sweet taste?

A

electronegtive elements in molecules

common elements are O and N:

  • O: alcohols (glycerols and glucose), aldehydes, cinnamaldehyde
  • N: peptides and amino acids
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4
Q

what is used as a reference for sweetness of sugars?

A

glucose

assigned number 1

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5
Q

what sugars are the same sizes but different levels of sweetness?

A

lactose and sucrose

glucose and fructose

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6
Q

what are the two groups of amino acids? what are these groups based on?

A

D and L amino acids

based on their optical activities (one rotates clockwise and the other rotates anticlockwise)

this results in differences due to interactions in the mouth receptors

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7
Q

are D or L amino acids sweeter?

A

D is always sweeter than L

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8
Q

how is sucrose broken down?

A

invertase breaks down glucose and fructose bond

results in a mixture of glucose and fructose, which is sweeter than the solution of sucrose (known as invert sugars)

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9
Q

what monosaccharides compose sucrose?

A

glucose and fructose

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10
Q

what are invert sugars?

A

broken down components of sucrose (glucose and fructose)

glucose and fructose (the invert sugars) are sweeter than the original sugar

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11
Q

what does amylase break down in corn syrup?

A

glucose hydrolysate

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12
Q

what is high fructose corn syrup broken down into?

what enzyme does this?

A

glucose isomerase breaks down fructose into hydrolysate, comprised of glucose and fructose

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13
Q

what are traditional sweeteners?

A 
sucrose (regular sugar)
invert sugars
corn syrup
high fructose corn syrup (HFCS)
maltodextrose
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14
Q

what are examples of food used traditionally as sweeteners?

A

honey
maple
molasses

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15
Q

what compounds are found in honey?

A

fructose (33-40%)
glucose (32-40%
water (15-20%)
significant phenolic content

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16
Q

what sugars are found in maple?

A

glucose
fructose
sucrose

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17
Q

what are molasses?

A

dark syrup liquid left after recovery of sugar from either sugar cane or sugar beet

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18
Q

describe how molasses are made

A
  1. crush sugar cane to create juice. Heat juice to concentrate. Separate sugar crystals and syrup (molasses)
  2. continue to heat syrup. Separate into crystals and syrup (cane molasses)
  3. continue to heat. Separate into crystals and another syrup (black syrup molasses)
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19
Q

how does the color and viscosity change as you keep heating molasses syrup?

A

they increase

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20
Q

what is found in sugar cane?

A 
vit B6
iron
Mg
K
manganese
calcium
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21
Q

high intensity synthetic sweeteners are ____ and ____ than traditional sweeteners

A

cheaper: easy production

less caloric: synthetic sweeteners are not as readily metabolized

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22
Q

what is the result of synthetic sweeteners not being as readily metabolized?

A

less calories

mouth bacteria don’t break them down to acids, which cause decay

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23
Q

what are factors that affect sweetener use?

A
  • cost
  • calories
  • sweeter equivalence with
  • sugar (isosweetness)
  • solubility and viscosity (must be H2O soluble and dissolve at the same rate)
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24
Q

order the polyols according to relative sweetness

A
  1. xylitol (isosweet with sucrose)
  2. malitol
  3. manitol
  4. sorbitol
  5. isomalt
  6. polyextros
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25
Q

what sweetener is isosweet as sucrose?

A

xylitol

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26
Q

what is synergy

A

mixing multiple sugars and sweeteners (who have different viscosity and sweetness) together in solution

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27
Q

what are polyols?

A

polyhydric alcohols

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28
Q

what are common food products that use synergy? what is their ratio used?

A

chewing gum: 3:2 xylitol to sorbitol

sugar free products: 4:1 ratio of maltitol and xylitol

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29
Q

which is the sweetest polyol?

A

xylitol

isosweet to sucrose

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30
Q

does polyol have an aftertaste?

A

no

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31
Q

why is xylitol useful for diabetes?

A

metabolized independently of insulin

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32
Q

why is xylitol resistant to fermentation of oral bacteria?

A

they don’t cause pH decline (as with sucrose) to demineralize tooth enamel and cause decay

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33
Q

why is xylitol considered low calorie?

A

it is not metabolized in the gut

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34
Q

main properties of xylitol?

A
  • sweetest polyol (isosweet to sugar)
  • has no discernible aftertaste
  • metabolized independently of insulin
  • resitant to fermentation by oral bacteria
  • bacteriocidal
  • stable to heat (good for baked goods)
  • doesn’t react with AA (no browning occurs)
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35
Q

why does xylitol not cause browning in foods?

A

it does not react with amino groups or compounds, thus it does not lead to non-enzymatic browning reactions

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36
Q

what are examples of products manufactured with xylitol?

A 
candies
gums
diabetic food
oral hygiene products
pharmaceutirals
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37
Q

what is the effect of polyol consumption?

A

since they are not readily metabolizked, too much intake can lead to enhanced bowel movement

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38
Q

what are types of high intensity sweeteners?

A
  1. natural

2. synthetic

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39
Q

compare D and L synthetic high intensity sweeteners

A

D: insipid (tasteless)
L: sweeter

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40
Q

compare D and L natural high intensity sweeteners

A

D: sweeter than L (like usual)
L: insipide (tasteless) or bitter

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41
Q

what are 4 examples of natural sweeteners

A

glycine
d-tryptophan
miraculin
ketemfe

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42
Q

what is special about glycine?

A

does not have a chiral carbon

thus, no D or L forms

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43
Q

how much sweeter is D-tryptophan than sucrose?

A

30 to 40 times sweeter

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44
Q

what is beta-chloro-6-tryptophan

A

derivative of D-tryptophan

1500x sweeter than sucrose

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45
Q

what is miraculin

A

berry in west africa

if eaten by itself, it is bland. If you eat anything else after (even bitter or sour foods), it will taste sweet

gives an effect of taste modifiation

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46
Q

what is a food that creates taste modification?

A

miraculin

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47
Q

what is ketemfe

A

a fruit that produces a peptide rich hydrolysate which is several time sweeter that sucrose

the hydrolysate is known as thaumatin

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48
Q

what is thaumatin

A

the hydrolysate produced in ketemfe, which is several times sweeter than sucrose

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49
Q

what is stevia

A

shrub found in sub-tropical and tropical zones in south america

several times sweeter than sucrose

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50
Q

what is the active compound in stevia?

A

glycosides of steviol (an alcohol)

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51
Q

what are 3 examples of synthetic sweeteners?

A

aspartame

acesulfame potassium

sucralose (aka splenda)

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52
Q

what are 3 examples of synthetic sweeteners?

A

aspartame

acesulfame potassium

sucralose (aka splenda)

saccharin

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53
Q

what is aspartame commercially known as?

A

equal

nutrasweet

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54
Q

what products is aspartame commonly found in?

A

gums
yogurts
beverages

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55
Q

how much sweeter is aspartame compared to sucrose?

A

200 times

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56
Q

why is aspartame not suitable for cooked or baked products?

why is it harmful when exposed to heat?

A

it is heat labile

high heat can cause aspartame to break down into components (methanol is harmful)

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57
Q

what is the defective enzyme in PKU? What is PKU?

A

PKU is phenylketonuria

defective enzyme is phenylalanine hydrolase

This results in phenylalanine not being utilized, thus it will accumulate and cause mental disorders

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58
Q

which sweetener must be used in combination with other sweeteners?

A

acesulfame potassium

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59
Q

can acesulfame potassium be used in heat?

A

yes because it is heat stable

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60
Q

how is acesulfame potassium found in markets?

A

in the form of tablets

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61
Q

what is saccharine?

A

Na salt + Cl salt

62
Q

what is saccharine? why was it not permitted for human consumption until recently?

A

a synthetic sweetener

it was shown to cause tumors in bladders of rats

63
Q

can saccharin be used in cooked and baked products?

A

yes, it is heat stable

64
Q

what is the brand name for sucraloase?

A

splenda

65
Q

what form is sucralose (aka splenda) found in supermarkets?

A

sachets or granulated forms

66
Q

describe the chemical structure of sucralose in comparison to sucralose

A

it is the trichloro derivative of sucrose

heat stable

67
Q

out of all synthetic sweeteners, which ones are heat stable and which are not?

A

heat stable: acesulfame-K, saccharin and sucralose

no: aspartame

68
Q

how much sweeter is sucralose than sucrose?

A

6000x sweeter

69
Q

why is sucralose not “caloric”?

A

it is not metabolized in the gut and does not supply calories as sugar

70
Q

what chemical components creates a salty taste? what reactions are they formed in?

A
  • salt ions (Na+, K+, Cl-)
  • formed in neutralization reactions
  • salty taste is dependent on the size of ions (smaller ions are salty, larger ions are bitter)
71
Q

smaller salt ions are ____ and larger ions are _____

A

salty

bitter

72
Q

CsCl, KI, MgSO are ____ ions

A

bitter

73
Q

PbAC and BeAc are ____ ions

A

sweet

74
Q

LiCl, LiBr, NaNO, KCl are ____ ions

A

salty

75
Q

what are functions and uses of NaCL?

A
  • imparts salty taste
  • preserves food
  • flavor enhancer
  • source of electrolytes
  • enhances production of stomach acid (stimulates and aids digestion)
76
Q

how does salt act to preserve food?

A

salt decreases water activity = microbial activity will decrease = enzymatic activity decreases because enzymes are covered in a layer of salt

77
Q

how much NaCl can people tolerate? what happens when food has higher than this percent?

A

2%

beyond this, NaCl may render the product indigestible or nauseating

78
Q

what are health issues related with NaCl consumption?

A

hypertension

high blood pressure

79
Q

what are ways to reduce NaCl levels in food?

A
  1. addition of spices
  2. salt substitues
  3. replacing Na compounds with compounds of other cations (eg. KHCO3 instead of NaHCO3)
80
Q

what are types of salt substitutes?

A

mineral based subs: salt of ions other than Na+ (eg, K+ and NH4+) to stimulate NaCl in taste

vegetized salt substitutes: powdered dehydrated vegetables as a base

81
Q

what are examples of commercial salt substitutes?

A 
NH4Cl
KCl
citric acid
citrates
starch
glutamic acid
glutamates
82
Q

what are the 3 classes or organic compounds responsible for bitternesS?

A

alkaloids
glycosides
peptides (with hydrophobic and aromatic characteristics)

83
Q

what are alkaloids

A
  • one class of organic compounds responsible for bitterness
  • nitrogenous
  • widely distributed in plants
84
Q

what are examples of alkaloids?

A

quinine

caffeine

theobromine

85
Q

what is quinine

A
  • an alkaloid (exhibits bitter tastes)
  • white amorphous powder
  • limited solubility in H2O
  • one of the most bitter substances known
  • used in beverages
86
Q

describe the solubility of quinine

A

limited solubility in H2O

87
Q

what is one of the most bitter substances known?

A

quinine

88
Q

what is caffeine?

A
  • crystalline purine derivates found in coffee beans, tea leaves and cola nuts
  • solubility in H2O is 1:50 at room temp or 1:2 at 65degc
  • stimulant wit GRAS status
89
Q

what is theobromine? what is it structually related to? where is it found?

A
  • related to caffeine

- found with caffeine in various flants (eg. cocoa beans and cola nuts)

90
Q

what are glycosides?

A
  • creates bitter tastes

- aglycones esterified with various sugars

91
Q

what are examples of glycosides?

A

narigin
hesperidin
coniferin
sinigrin

92
Q

what is narigin

what is it found in?

A
  • a glycoside (causes bitter tastes)
  • found in grapefruit and bitter orange
  • one of the most bitter substances known
93
Q

what does the hydrolysis of narigin yield?

A

d-rhamnoglucose and glycone

94
Q

what is hesperidin? what is it found in?

A
  • a glycoside (causes bitter tastes)

- found in sweet orange and citrus fruits

95
Q

what does the hydrolysis of hesperidin yield?

A

yields rutinose and aglycone hesperetin

96
Q

what is coniferin? where is it found?

A
  • a glycoside (causes bitter tastes)

- found in conifer wood

97
Q

what does the hydrolysis of coniferin yield?

A

coniferyl alcohol, which can be further oxidized to vanillin

98
Q

what compound is vanillin oxidized from?

A

coniferyl alcohol, which is a product of the hydrolysis of coniferin

99
Q

what is sinigrin?

A

black mustard seeds

100
Q

what does the hydrolysis of sinigrin yield?

A

glucose and allyl isothiocyanate

101
Q

which compound makes taste buds insensitive to sweet and bitter?

A

gymnemic acid

102
Q

what is the miracle fruit?

how does this compound work?

A

makes bitter and sour compounds taste sweet, eve though it was tasteless by itself

it inhibits the bitter or sour taste to sweet molecules

103
Q

what are two criteria to taste sensitivity of sweet molecules??

A

solubility: the sweet molecules must be in saliva to interact with the sweet receptors. Thus, it must be able to be soluble in saliva
concentration: need to have a threshold value to be perceived as sweet

104
Q

compare the taste and smell threshold level of the taste sensitivity of sweet molecules

A

taste has a higher threshold value

105
Q

what can salt in a food enhance?

A

acid in a food (eg. adding salt to grapefruit)

sweet taste

106
Q

what are the 3 components of mouthfeel?

A

pain
temperature
tactile sensations

107
Q

describe how food will influence mouthfeel via pain

what compounds do this?

A

when compounds in foods interact with pain receptors in mouth and mucous membrane to cause irritation and pain

compounds: zingerone, gingerol, shagol, ally isothiocyanate

108
Q

describe how food will influence mouthfeel via hot temperature

A

volatile compounds will leave product and interact more effectively with taste receptors

molecules move vigorously and interact again more effectively

109
Q

describe how food will influence mouthfeel via cold temperature

A

molecules interact less effectively

can cause numbness

110
Q

what are tactile sensations? what does it allow for?

A

allows feeling of texture, astringency and consistency

111
Q

what are flavor enhancers?

what are examples?

A

compounds that improve or intensify flavour quality in foods

eg. MSG and maltol

112
Q

how does maltol act as a flavour enhancer?

where/how is it formed?

A
  • maltol is one of the products formed in the caramelization of sugar
  • produces the “nutty” taste”
  • used in enhancing flavour in baked goods
113
Q

sub-threshold levels of salt reduces ____ in foods

A

sourness

114
Q

sub-threshold levels of acids reduces ____ in foods

A

saltiness

115
Q

sub-threshold levels of sugar reduces ____ in foods

A

saltiness

116
Q

what methods are used with taste panelling in sensory evaluation?

A

preference and difference testing

117
Q

describe preference panel taste testing

what is it most useful in?

A

choosing foods we prefer over others

most useful in food product development where large segments of population is used to verify product acceptability

118
Q

what are the 3 kinds of preference taste testing

A
  1. simple paired comparison test
    2 hedonic scale
  2. ranking test
119
Q

describe the simple paired comparison test

A

a pair of samples is provided to panel and are asked to select the one they prefer in terms of a particular attribute

120
Q

describe the hedonic scale (type of preference taste panel)

A

a point system used to verify degree of likeness or dis-likeness of a product. (like extremely, like very much, like moderately, like slightly, neutral, dislike slightly, dislike moderately, etc…)

121
Q

describe the ranking test (type of preference taste panel)

A

panel is provided with more than 2 samples and asked to rank them in order of preferences

122
Q

what is difference testing?

A

verifying differences in particular attributes (eg firmness, juiciness, etc…) in a food product

123
Q

what are the 6 kinds of difference testing?

A 
1. simple paired comparison test
2 scheffe's paired comparison test
3. multiple paired comparison test
4. triangle test
5. duo-trio test
6. ranking test
124
Q

describe the scheffe’s paired comparison test

A

similar to the simple paired comparison test, except that panel is asked to indicate or quantify degree of difference

125
Q

describe the multiple paired comparison test

A

3 or more samples are compared against one another (A,B,C,D)

A with B
A with C
A with D
etc…

126
Q

describe the triangle test

A

panel is presented with 3 samples and told that 2 of them are identical and required to pick the odd one

127
Q

describe the duo trio test

A

similar to triangle test. Panel is presented with 3 samples and one is given as a reference. Eg. A, B, C. If C is given as the reference, the panelist must choose which two are the same and which is the odd one

128
Q

compare the duo-trio and the triangle test. which is better?

A

Triangle test is better because the probability of choosing the right one is lower than in duo-trio test

129
Q

what are the seven primary odors?

A
  1. Ethereal: thin rod-shaped molecules
  2. Camphoraceous: hemispherical-shaped molecules
  3. Musky: flat disk shaped;10A in diameter
  4. Floral: shaped as keyholes
  5. Minty: wedge-shaped molecules
  6. Pungent: negatively charged molecules
  7. Putrid: positively charged molecules
130
Q

what ions cause sour taste/tartness?

A

H+ ions from acids (eg. lactate, pyruvate, acetate…)

131
Q

what determines the degree of sourness?

what is it not determined by?

A

H+ concentration

not determined by total acidity of food

132
Q

how might a food affect the perception of sourness?

A

components in a food might interact with the H+ ions, and change the perception of sourness

133
Q

what are other factors that affect sour taste, besides H+ ion concentration?

A

nature of acidic group
buffering capacity
presence of other compounds

134
Q

what are 3 ways that acid is important in food?

A
  1. preservation
  2. imparts flavor
  3. stabilizes products
135
Q

what are 2 ways that acid is used for preservation?

A
  1. lowers pH: creates an environment that is less condusive to growth of microorgansms and restrict enzymatic activity
  2. enhances natural antioxidants by acting as metal ion chelators
136
Q

how does acid affect vitamin C?

A

acid causes vitamin C to behave like an antioxidant in its reduced state (ketoascorbic acid)

137
Q

what is the reduced state of vit C?

A

ketoascorbic acid

138
Q

what is an example of acidity imparting flavor in foods?

A

wine

139
Q

what are inorganic acids used in foods?

A

H3PO4 (phosphoric acid)

HCl (hydrochloric acid)

140
Q

the majority of acids used in foods are….

what are examples?

A

organic acids:

  • acetic
  • citric
  • fumaric
  • lactic
  • tartaric
  • malic
  • benzoic
  • scorbic
141
Q

describe acetic acid

what flavor does it give in foods?

A
  • sharp and piquant. Clear and colorless

- gives aromitc flavor

142
Q

how is acetic acid commercially prepared?

A
  1. by oxidation of CH3CHO (acetaldehyde) or butane

2. yeast fermentation of fruit juices, sucrose, glucose, malt…

143
Q

what is the most abundant organic acid in fruits and veg?

A

citric acid

144
Q

what are the characteristics of citric acid?

A
  • white crystalline powder
  • no smell
  • very soluble in H2O and alcohol
  • can be used to replace vinegar because it has no odor
145
Q

what can be used to replace acetic acid?

A

citric acid

because it has no odor

146
Q

what are characteristics of lactic acid?

A
  • pale, yellow, viscous liquid

- pungent smell

147
Q

what products is lactic acid used in?

A

milk and dairy

148
Q

what are characteristics of fumaric acid?

A
  • odorless, white granular or crystalline powder
  • sparingly soluble in H2O
  • soluble in ethanol
149
Q

how is fumaric acid produced?

A

produced during fermentation of glucose of molasses by Rhizopus species

150
Q

what is fumaric acid most used in?

A

food products where solubility is not a significant quality

151
Q

what is scorbic and benzoic acid used mostly fod?

A

food preservation

152
Q

scorbic and benzoic acid can be in what forms?

A
  1. free form

2. salt form (K, Na, Ca salts)

Food Chemistry 2 (4 decks)

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